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Audio Interfaces
An audio interface '''is a hardware device that allows you to attach a real-world instrument or audio device to the input of an iOS device. There are two primary types of audio interfaces: *A '''line-in interfaces is an hardware devices that essentially adapts an instrument's analog audio output to the analog line input of an iOS device. *A digital audio interface (DAI, or USB interface) is a hardware device that allows you to convert an analog audio input (guitar, microphone, keyboard, etc) to a digital output (USB, Dock Connector, etc). Aside from using the onboard microphone, an audio interface of some kind is required to record analog audio to iOS devices. Examples of audio interfaces include the Peavey AmpLink, Amplitube iRig, Focusrite iTrack Solo, and Akai EIE. Note that an audio interface is not the same as a MIDI Interface, which routes MIDI data between hardware devices. For information on specific audio interfaces and their iOS compatibility, see List of Audio Interfaces Line-In Interfaces Line-in interfaces are audio interfaces that plug into the iOS device through its headphone/microphone combination jack. These are not technically digital audio interfaces, as the signal chain is analog until it reaches the iOS device tself, but for the purposes of the iOS musician they can still be classified as an audio interface in the sense that they allow you to record a real-world instrument on your iOS device. Advantages *'Price.' Line-in interfaces are typically much more inexpensive than even basic digital (USB) interfaces, as they have minimal internal electronics and features. *'Simplicity. '''Most line-in interfaces include simply an input jack for your instrument (i.e., guitar cable), a headphone jack for monitoring, and the line-out plug to attach to the iOS device's input jack. *'Portability. Most line-in interfaces are passive, requiring no additional power supply, or are battery-operated, meaning that it takes up very little space, is easy to cable & connect, and can be taken & used almost anywhere. *'Compatibility. '''Line-in interfaces are compatible with ''all iOS devices, as they do not require special USB/CCK adapters that are compatible with iPads only. Disadvantages *'''Sound quality **Most line-in interfaces rely on the iOS device's internal amplifier to process the input signal, which is not designed for accurate instrument processing. This leads to a somewhat noisy signal, heard in the form of hiss or distortion, especially with high gain levels. Some line-in interfaces have active circuitry designed to pre-amplify and process the signal to make it cleaner, but these are typically inferior than a dedicated digital audio interface. **Additionally, a significant drawback to a line-in interface is feedback introduced from the line-in jack on the iOS device. The combination headphone/microphone jack is a basic TRS (tip/ring/sleeve) 4-position jack. The close proximity of the signal connectors on the TRS jack means high-gain input (such as an amplified guitar signal) with realtime monitoring through the same jack (headphones) introduces signal feedback across the TRS connectors, which can be quite severe. Low-gain instruments and recordings are typically unaffected, but an overdriven lead guitar, for instance, could cause significant feedback and loss of quality in the recording. *'Features.' Line-in interfaces usually allow for only one input, with few or no controls over gain or amplification. Singal monitor for gain or clipping is absent, as are connectors for a wider array of input devices. Examples of line-in audio interfaces are the Peavey AmpLink, the IK Multimedia iRig, and the Tascam iXZ (a particularly feature-rich line-in interface). Digital Audio Interfaces True digital audio interfaces (DAI) connect to the iOS device via a digital connection. Typically, a DAI will have a USB output (mini-USB, micro-USB, or USB type-B female jack), to which you can connect the iOS device via Apple's Camera Connection Kit (CCK)or USB Camera Adapter. For more information on connecting digital interfaces and controllers to an iOS device, see USB Inputs. Advantages *'Sound quality.' The internal amplifier electronics in a dedicated DAI are typically far superior than those of an iOS device, and are specifically designed for instrument signal processing. A good DAI will be able to provide the proper type and amount of input gain for a given instrument, and deliver that cleanly amplified analog signal out to the iOS device via an accurate digital interface. Problems of feedback/signal crosstalk and high noise floor are virtually eliminated. *'Features.' DAIs often include more advanced features such as multiple inputs, variety of input and output connection types (XLR, 1/4" TRS line/guitar-level inputs, RCA stereo, 1/8" stereo, etc), onboard mixing of signal levels, phantom power (+48V required for some microphones), signal level monitoring, monitor mix level controls, and so on. *'Versatility. '''A USB DAI can work not only with an iOS device but with a desktop or laptop DAW/recording software. Additionally, many USB DAIs also offer analog line-out for montoring and mixing, making it a useful tool outside of digital recording. Disadvantages *'Price.' While basic USB DAI prices can start as low or lower as a line-in interface, most DAIs with good featuresets, quality and reviews/ratings are significantly more expensive. *'Complexity. While the basic concept of connecting a USB DAI to an iOS device is simple (Instrument to DAI; DAI to iOS device over USB), the abundance of features can make connections confusing or require more cabling and adapters, and make troubleshooting connections more difficult. *'''Compatibility. USB DAIs may not be compatible with all iOS devices and all versions (ToDo - link to iOS Devices section showing CCK compatibility). Up through iOS 6, only iPads are compatible with the Apple Camera Connection Kit / USB Camera Adapter, which is required to connect the USB DAI to the iOS device. iPhones and iPod touches may ''support USB input by means of Jailbreaking and various hack methods, but it is not a truly supported platform. There are several DAI's designed specifically for direct connection to iPhone, such as the Apogee Jam, which overcome the limitation by using Apple approved accessory connection circuitry instead of USB. These are typically less complex than full-on USB DAIs, but just as high quality (and price). With iOS 7, however, iPhones will also work with the CCK USB adapter. *'Reliability. 'Whereas a line-in interface is a simple analog I/O device, a DAI is much more complex and could introduce disconnections in the signal chain. Additionally, there is an added strain to the system resources of the iOS device due to its processing the digital signal via the USB adapter/CCK. In some scenarios, the USB adapter must be unplugged and re-attached due to power draw issues or insufficient available system resources. This problem is less prevalent on newer iOS devices with more processing power, but reliability is a factor. *'Power & Portability. '''USB DAWs require some amount of active power. Some are efficient enough to operate only on the power provided through the iOS devices' dock connector, though this may prove unreliable (see above). Others allow for battery or AC (wall) power, or a combination of the three. In any case, USB DAIs are typically larger, with more needs for cabling and power than a basic line-in interface, and are therefore less portable in nature. What to Buy The decision of which audio interface to buy will be based entirely on your needs. If you are using an iPhone or iPod Touch (and are unwilling to hack/jailbreak), a simple line-in interface is your only option. iPad users can choose either a line-in or USB DAI. Users with very basic recording needs, such as for demos and quick sketches, should strongly consider a basic line-in interface for its cost, simplicity and portability. Those with more advanced needs, such as multiple inputs and fine-tuning of input and monitor levels are better served by a true DAI. If possible, consider buying both a simple, affordable line-in interface, such as the Peavey AmpLink, for portable work, and a more robust and feature-rich DAI for final, high-quality recordings or collaborative work with other performers. For a comparison list of popular iOS-compatible audio interfaces, see List of Audio Interfaces. Category:Hardware